IB Biology Heart Structure and Function

Circulatory System

consists of a heart that pumps a circulatory fluid through a network of vessels throughout a body.

Parts of a circulatory system in chordates

• Blood

• Heart

• Blood Vessels

Blood

• Transports oxygenated nutrients throughout the body

• Carries away waster products

• Helps to regulate body temp

• Protects the body by carrying immune cells and clotting factors

• Acts as a delivery system for hormones

Heart

A muscular organ that pumps blood throughout the body

Blood Vessels

Arteries, capillaries, and veins that carry blood throughout the body

Single circulation

circulatory system where blood flows through the heart once per cycle

Single Circulation Steps

1) Heart pumps blood to gills

2) Blood flows through capillaries in the gills. Oxygen in the water moving over the gills diffuses into the blood. Carbon dioxide diffuses from the blood into the water.

3) The oxygenated blood has enough pressure to flow from the gills to the rest of the body

4) While passing through tissue capillaries around the body, cells take the carbon dioxide from the blood and add oxygen

5) Deoxygenated blood then returns to the heart for pumping to the gills

In a single ciruclatory system, the heart has _______ chambers

1 atrium, 1 ventricle

Double circulation

circulatory system where blood flows through the heart twice per cycle and has two different circuits

Double circulation steps

1) The rights side of the heart pumps deoxygenated blood to the lungs.

2) Blood flows through the capillaries in the lungs. The blood must be at a low pressure to avoid the capillaries bursting. Oxygen diffuses in, carbon dioxide out.

3) After flowing through the alveolar capillaries, the blood pressure is too low to continue flowing to all the other organs of the body, so the oxygenated blood returns to the heart to be re-pumped

4) The left side of the heart pumps oxygenated blood to all the other tissues in the body

5) While passing through tissue capillaries around the body, cells take the oxygen and add carbon dioxide

6) Deoxygenate blood returns to the heart

Atria

Upper chambers of the heart that receive blood from the veins and pump it to the ventricles so that the ventricles fill as soon as possible after contraction

Ventricles

Lower chambers that pump blood out through arteries

Septum

a muscular wall that divides the heart into two sides, prevents deoxygenated and oxygenated blood from mixing

Pulmonary Artery

Carries deoxygenated blood out of the right ventricle of the heart to the pulmonary circulation

Aorta

Carries oxygenated blood out of the left ventricle of the heart to the systemic circulation

Pulmonary Veins

There are four pulmonary veins, two from each lung. They carry oxygenated blood from the lungs to the left atrium of the heart

Vena Cava

• Superior + Inferior

• They carry deoxygenated blood from the body to the right atrium

Coronary arteries

Branch directly from the aorta to deliver oxygenated blood to the heart muscle

Cardiac Veins

Collect deoxygenated blood from the heart muscle, merge, and empty it into the right atrium

Electrical Conduction System

Synchronizes contractions since the system spreads electrical impulses

Cardiac Muscle Cells

Branching and intercalated disks that enable rapid electrical signal transmission between individual cells

Left Ventricle Wall

Thicker than right ventricle since it needs to pump blood throughout the body

Right Ventricle Wall

Pumps blood to the lungs, which requires less force and less force is needed for efficient gas exchange

Atrioventricular Valves

Between atria and ventricles are open to allow blood to flow from atria to ventricles but close to prevent blood from moving back

Semilunar Valves

Open to allow blood to flow from the ventricles into the artery but close to prevent the blood from moving back into the ventricle

Branching and intercalated disks enable

rapid transmission of electrical impulses between cells, enabling coordinated contraction of the heart

Intercalated disks function

• The junctions contain proteins that provide strong mechanical adhesion between cells, preventing them from separating during contraction

• The ease of ion movement at the intercalated discs permits action potentials to transmit from one cardiac muscle cell to the other with little resistance

Myogenic

The muscle contraction originates in the heart itself, rather than being triggered by a nerve impulse

Cardiac pacemaker cells are located in the

right atrium

Steps of an electrical impulse in the heart

1) The sinoatrial node initiates the cardiac cycle by generating an electrical impulse at a regular rate

2) The impulse spreads throughout the walls of the atria, causing the right and left atria to contract

3) Situated at the junction between the right atria and ventricle, the atrioventricular node delays the electrical impulse to allow blood to flow from the atria to the ventricles

4) A thick bundle of cells extends through septum from the AV node into the ventricles. The bundle divides into branches that carry the electrical impulse into the ventricles

5) Purkinje fibres extend from the branches into the ventricular muscle, causing contraction

Systole

• The contraction of the heart muscle

• The period when the heart chambers are pushing blood

Diastole

• The relaxation of the heart muscle

• The period when the heart chambers fill with blood

The cardiac cycle is a sequence of actions that

generate one pump of the heart

During a cardiac cycle, pressure within the ventricles significantly increases during contraction then

rapidly decreases as the ventricles relax

When ventricular pressure surpasses atria pressure, the atrioventricular values

close, preventing blood from flowing back towards the atria

When ventricular pressure exceeds pressure in the pulmonary artery and aorta, the semilunar valves

open to eject blood

When ventricular pressure is lower than the pressure in the pulmonary artery and aorta, the semilunar valves

• close, preventing blood from flowing back to the ventricles

Pulse is measured in

beats per minute

Factors affecting pulse rate include

• Age- decreases with age

• Exercise- increases during exercise

• Stress- Increases

• Medications- Increase or decrease

• Temperature- High temps increase

• Health Conditions- Cause abnormal ones